I have a pair of eng. budgies and next to them in sep cage amer. budgies(pair)?

my americans are about 4 mths old, and sit and preen feed each other, i bought them from a private breeder who thought they were hen/, but i still cannot tell, they both look like s to me, the cere on both seem to be the same color blue/purple. also i have a pair of eng. budgies in a separate cage, no doubt about the of the eng. but they act like a grumpy old married couple about to divorce, i have never seen them feed one another. my female english is smitten with one of my amer. they sit and stare at each other. should i fix it so they cannot see one another? or put them all together and see who falls in love? confused. i know people cross breed the two budgies but i hate to cause and affair to occur...lol