i got my first two yorkies only a few days apart. i got a boy and girl
they were not littermates and they did not come from the same breeder
the girl was older (she was around 13 weeks and the boy was around 9 weeks). oh my gosh, they grew up so nicely together and had so much fun. they played, snuggled, did everything together. i do not regret doing it this way at all
the only "negatives" i can think of are:
1. it was harder to potty train because if i did not catch them in the act, i did not know which one did it. which means i did not know which one needed to be watched more
2. all their vetting is really close together which means double the cost. now that i have more babies, the newer ones are spaced out more. but the vetting at the beginning was pretty costly because there were two of them needing the same things
i have read that people worry that the babies will bond more with each other than to their humans if you get them at the same time but i never found that to be the case with mine. they love both me and my fiance
good luck with whichever you choose!!