Before I got my little girl Becca, I had only had one at any time.
My Male Sneakers was two years old, when I decided to get Becca.
I don't have the words to tell you, how profoundly it changed Sneakers, it seemed to "mature" him over night. Two things did that (I think), those
being that he thought Becca was his Puppy, and, that she was Female.
I will never have less than two again !
They play, maintain each other, and are just inseparable, mainly because
Becca sees Sneakers as her teacher/leader, and his patients with her
puppyness is monumental, which includes giving her food out of his mouth.
So, in my opinion...
Definitely two,
Same breed,
Two years apart, and
opposite sex.
Have a good Day !
S.W.