found a pup last night

i have a one year old hyperactive pit and yesterday i found a dober man pup... my pit is male and the doberman pup is female... my pit tries and has tried to ...let say dominate her sexually...but she is to small she looks like she is 2 months old... but i really dont know.. ive decided to keep them seperate for now.. i think hes getting jealous because he'll come and sit practically on me and my wife when ever we pet the new pup. for now her name is morena ..my pits name is buster