If you want to remember the same target and home on it even when others get closer you could do it like this
Make missle have a private variable called target, with a default of -1
For each missle,
------if target is equal to -1
-----------enemyfamily. - pick closest to missle.x,missle.y
------------------missle, set 'target' to enemyfamilt.uid
For each missle
------if target is not equal to -1
----------enemyfamily, pick by unique id missle('target')
-------------------missle(with bullet behavior). Set angle toward enemyfamily
This would make each missle target one enemy and stick with it till the end, though it'll be a bit trickier if you don't want two missles to ever target the same one