diff --git a/R/join_keys.R b/R/join_keys.R
index bca055f1b..52563c9b8 100644
--- a/R/join_keys.R
+++ b/R/join_keys.R
@@ -227,8 +227,6 @@ c.join_key_set <- function(...) {
 #' @param i index specifying elements to extract or replace. Index should be a
 #' a character vector, but it can also take numeric, logical, `NULL` or missing.
 #'
-#' @param keep_all_foreign_keys (`logical`) flag that keeps foreign keys and other
-#' datasets even if they are not a parent of the selected dataset.
 #'
 #' @export
 #'
@@ -244,7 +242,7 @@ c.join_key_set <- function(...) {
 #' jk["ds1"]
 #' jk[1:2]
 #' jk[c("ds1", "ds2")]
-`[.join_keys` <- function(x, i, keep_all_foreign_keys = FALSE) {
+`[.join_keys` <- function(x, i, j) {
   if (missing(i)) {
     return(x)
   }
@@ -253,13 +251,31 @@ c.join_key_set <- function(...) {
     return(new_join_keys()) # replicate base R
   }
 
+  if (!missing(j)) {
+    checkmate::assert(
+      combine = "or",
+      checkmate::check_string(i),
+      checkmate::check_integerish(i, len = 1),
+      checkmate::check_logical(i, len = length(x))
+    )
+    checkmate::assert(
+      combine = "or",
+      checkmate::check_string(j),
+      checkmate::check_integerish(j, len = 1),
+      checkmate::check_logical(j, len = length(x))
+    )
+
+    subset_x <- update_keys_given_parents(x[union(i, j)])
+    return(subset_x[[i]][[j]])
+  }
+
   checkmate::assert(
     combine = "or",
-    checkmate::check_integerish(i),
-    checkmate::check_logical(i),
-    checkmate::check_character(i)
+    checkmate::check_character(i, max.len = length(x)),
+    checkmate::check_integerish(i, max.len = length(x)),
+    checkmate::check_logical(i, len = length(x))
   )
-  checkmate::assert_logical(keep_all_foreign_keys, len = 1)
+
 
   # Convert integer/logical index to named index
   if (checkmate::test_integerish(i) || checkmate::test_logical(i)) {
@@ -286,9 +302,6 @@ c.join_key_set <- function(...) {
     }
 
     ix_valid_names <- names(x[[ix]]) %in% c(queue, bin)
-    if (keep_all_foreign_keys) {
-      ix_valid_names <- rep(TRUE, length(names(x[[ix]])))
-    }
 
     new_jk[[ix]] <- x[[ix]][ix_valid_names]
 
@@ -312,8 +325,16 @@ c.join_key_set <- function(...) {
 #' - `[<-` is not a supported operation for `join_keys`.
 #'
 #' @export
-`[<-.join_keys` <- function(x, i, value) {
-  stop("Can't use `[<-` for object `join_keys`. Use [[<- instead.")
+`[<-.join_keys` <- function(x, i, j, value) {
+  if (missing(j)) {
+    stop("Can't use `[<-` for object `join_keys` with only i. Use [[<- instead.")
+  }
+
+  checkmate::assert_string(i)
+  checkmate::assert_string(j)
+
+  x[[i]][[j]] <- value
+  x
 }
 
 #' @rdname join_keys
@@ -341,7 +362,7 @@ c.join_key_set <- function(...) {
     combine = "or",
     checkmate::check_string(i),
     checkmate::check_integerish(i, len = 1),
-    checkmate::check_logical(i, len = 1)
+    checkmate::check_logical(i, len = length(x))
   )
   checkmate::assert_list(value, names = "named", types = "character", null.ok = TRUE)
   if (checkmate::test_integerish(i) || checkmate::test_logical(i)) {
@@ -436,7 +457,6 @@ length.join_keys <- function(x) {
   sum(vapply(x, function(.x) length(.x) > 0, logical(1)))
 }
 
-
 #' @rdname join_keys
 #' @export
 format.join_keys <- function(x, ...) {
@@ -445,7 +465,7 @@ format.join_keys <- function(x, ...) {
     my_parents <- parents(x)
     names_sorted <- topological_sort(my_parents)
     names <- union(names_sorted, names(x))
-
+    x_implicit <- update_keys_given_parents(x)
     out <- lapply(names, function(i) {
       this_parent <- my_parents[[i]]
       out_i <- lapply(union(i, names(x[[i]])), function(j) {
@@ -466,6 +486,18 @@ format.join_keys <- function(x, ...) {
           if (length(keys) == 0) "no primary keys" else toString(keys)
         )
       })
+
+      implicit_datasets <- setdiff(names(x_implicit[[i]]), names(x[[i]]))
+      if (length(implicit_datasets) > 0) {
+        out_i <- c(
+          out_i,
+          paste0(
+            "  --* (implicit via parent with): ",
+            paste(implicit_datasets, collapse = ", ")
+          )
+        )
+      }
+
       paste(out_i, collapse = "\n")
     })
     paste(
diff --git a/R/parents.R b/R/parents.R
index b68b3a02e..d7ad1bafe 100644
--- a/R/parents.R
+++ b/R/parents.R
@@ -110,6 +110,7 @@ parents.teal_data <- function(x) {
 #'   ADTTE = teal.data::rADTTE,
 #'   ADRS = teal.data::rADRS
 #' )
+#'
 #' parents(td) <- list("ADTTE" = "ADSL") # replace existing
 #' parents(td)["ADRS"] <- "ADSL" # add new parent
 `parents<-.teal_data` <- function(x, value) {
@@ -133,7 +134,7 @@ update_keys_given_parents <- function(x) {
   duplicate_pairs <- list()
   for (d1 in datanames) {
     d1_pk <- jk[[d1]][[d1]]
-    d1_parent <- parents(jk)[[d1]]
+    d1_parent <- parent(jk, d1)
     for (d2 in datanames) {
       if (paste(d2, d1) %in% duplicate_pairs) {
         next
@@ -149,8 +150,22 @@ update_keys_given_parents <- function(x) {
           # second is parent of first -> parent keys -> second keys
           d2_pk
         } else if (identical(d1_parent, d2_parent) && length(d1_parent) > 0) {
-          # both has the same parent -> parent keys
-          jk[[d1_parent]][[d1_parent]]
+          # both has the same parent -> common keys to parent
+          keys_d1_parent <- sort(jk[[d1]][[d1_parent]])
+          keys_d2_parent <- sort(jk[[d2]][[d2_parent]])
+
+          common_ix_1 <- unname(keys_d1_parent) %in% unname(keys_d2_parent)
+          common_ix_2 <- unname(keys_d2_parent) %in% unname(keys_d1_parent)
+
+          if (all(!common_ix_1)) {
+            # No common keys between datasets - leave empty
+            next
+          }
+
+          structure(
+            names(keys_d2_parent)[common_ix_2],
+            names = names(keys_d1_parent)[common_ix_1]
+          )
         } else {
           # cant find connection - leave empty
           next
diff --git a/man/join_keys.Rd b/man/join_keys.Rd
index 8e43beddc..85e9cd4e2 100644
--- a/man/join_keys.Rd
+++ b/man/join_keys.Rd
@@ -40,9 +40,9 @@ join_keys(x) <- value
 
 \method{c}{join_key_set}(...)
 
-\method{[}{join_keys}(x, i, keep_all_foreign_keys = FALSE)
+\method{[}{join_keys}(x, i, j)
 
-\method{[}{join_keys}(x, i) <- value
+\method{[}{join_keys}(x, i, j) <- value
 
 \method{format}{join_keys}(x, ...)
 
@@ -62,9 +62,6 @@ a character vector, but it can also take numeric, logical, \code{NULL} or missin
 
 \item{value}{(\code{join_key_set} or list of \code{join_key_set}) relationship pairs to add
 to \code{join_keys} list.}
-
-\item{keep_all_foreign_keys}{(\code{logical}) flag that keeps foreign keys and other
-datasets even if they are not a parent of the selected dataset.}
 }
 \value{
 \code{join_keys} object.
diff --git a/man/parents.Rd b/man/parents.Rd
index 54f75cf23..89e4cf7bd 100644
--- a/man/parents.Rd
+++ b/man/parents.Rd
@@ -57,6 +57,7 @@ td <- cdisc_data(
   ADTTE = teal.data::rADTTE,
   ADRS = teal.data::rADRS
 )
+
 parents(td) <- list("ADTTE" = "ADSL") # replace existing
 parents(td)["ADRS"] <- "ADSL" # add new parent
 }
diff --git a/tests/testthat/test-join_keys.R b/tests/testthat/test-join_keys.R
index 5a99a1020..6b9c9733c 100644
--- a/tests/testthat/test-join_keys.R
+++ b/tests/testthat/test-join_keys.R
@@ -110,7 +110,7 @@ testthat::test_that("[[.join_keys returns keys for given pair", {
     join_key("b", "a", "child-parent"),
     join_key("c", "a", "child-parent")
   )
-  testthat::expect_identical(my_keys[["b"]][["a"]], c(`child-parent` = "child-parent"))
+  testthat::expect_identical(my_keys["b", "a"], c(`child-parent` = "child-parent"))
 })
 
 testthat::test_that("[[.join_keys doesn't return keys for given a pair without explicit join_key", {
@@ -124,18 +124,33 @@ testthat::test_that("[[.join_keys doesn't return keys for given a pair without e
   testthat::expect_null(my_keys[["b"]][["c"]])
 })
 
-testthat::test_that("[[.join_keys infer keys between child by shared foreign keys to parent ", {
+testthat::test_that("[[.join_keys infer keys between child by equal (unordered) foreign keys to parent", {
   my_keys <- join_keys(
     join_key("a", "a", "aa"),
     join_key("b", "b", "bb"),
     join_key("c", "c", "cc"),
-    join_key("b", "a", "child-parent"),
-    join_key("c", "a", "child-parent")
+    join_key("b", "a", sample(letters[1:5])),
+    join_key("c", "a", sample(letters[1:5]))
   )
   parents(my_keys) <- list("b" = "a", "c" = "a")
-  testthat::expect_identical(my_keys[["b"]][["c"]], c(`child-parent` = "child-parent"))
+  testthat::expect_identical(my_keys["b", "c"], setNames(letters[1:5], letters[1:5]))
 })
 
+testthat::test_that(
+  "[[.join_keys infer keys between child by shared foreign keys to parent (key names are unique to datasets)",
+  {
+    my_keys <- join_keys(
+      join_key("a", "a", "aa"),
+      join_key("b", "b", "bb"),
+      join_key("c", "c", "cc"),
+      join_key("b", "a", c(aa = "bb")),
+      join_key("c", "a", c(aa = "cc"))
+    )
+    parents(my_keys) <- list("b" = "a", "c" = "a")
+    testthat::expect_identical(my_keys["b", "c"], c(bb = "cc"))
+  }
+)
+
 # [.join_keys -----------------------------------------------------------------
 testthat::test_that("[.join_keys returns join_keys object when i is missing", {
   my_keys <- join_keys(
@@ -170,23 +185,6 @@ testthat::test_that("[.join_keys returns join_keys object with keys for given in
   )
 })
 
-testthat::test_that("[.join_keys returns join_keys for given dataset including those connected with foreign keys", {
-  my_keys <- join_keys(
-    join_key("d1", "d1", "a"),
-    join_key("d2", "d2", "b"),
-    join_key("d3", "d3", "c"),
-    join_key("d2", "d1", "ab"),
-    join_key("d3", "d1", "ac")
-  )
-  testthat::expect_identical(
-    my_keys["d2", keep_all_foreign_keys = TRUE],
-    join_keys(
-      join_key("d2", "d2", "b"),
-      join_key("d2", "d1", "ab")
-    )
-  )
-})
-
 testthat::test_that("[.join_keys returns join_keys object for given dataset including its parent", {
   my_keys <- join_keys(
     join_key("d1", "d1", "a"),