Introducing young bantams to older larger flock

Hello I was given a bantam cochin rooster (Norman) and his sweet little girlfriend (pea, Old English Game Bantam)  a little over 2 weeks ago. (They'd been with my mom for a few weeks prior to that. Living in her garage). My  issue is that the flock just won't take to them( 4, 3 month old hens).  They have spent two weeks together separated in the same coop and have free ranged together.  Last night we tried the 'sneak them together at bed time' trick and it didn't work. The morning was chaos. Poor Norman and Pea took some hits. I have since separated them again  but am worried that they are too little to be accepted.  Norman has only tried to dominate our bottom hen (amercuna) but the other 3 (2 brahamas and 1 buff) are too big and bossy and he just runs from them.  Will he ever be either in charge or accepted.  I am pretty sure he's a little younger then my 4 large hens. I've done a ton of reading on various websites but they don't tell me much. I particularly worry about poor Pea she's so sweet and little.  She spends a lot of time jumping into my arms.  (The two brahamas are particularly bullysome.) Advice appreciated thank you.

Hi, that sounds like a pain to deal with.  So far, you've done what I would have done: separate but with contact and put them in at night.  I've never had bantams but I know they some of them can mate with regular hens.  I think the pullets are young, so not receptive, which may change.  He'll also get more confidence.  How old is he?

One thing I've done is have two coops fenced off so they get used to each other.  I then put the older chickens in with the young ones, so it was the younger chickens' coop.  I think the home-field advantage helped the younger ones.