We have a 4 dogs at home and we have another that lives with grandma (she has 10 acres and he needs the open space to run)
We have a female spayed mini schnauzer - 4yrs old
2 male yorkie/maltese full bro's diff litter - 23 months and 9 months old
1 female yorkie - 13 weeks old
I'd say if you don't have your male neutered nor plan to then get a female. One issue we have now is our male yorkies are trying to not only compete for alpha dominancy but they are going thru puberty so they are trying to mark everywhere even though they are fully pee pad trained!
It may take a couple of weeks to get all the dogs acclamated to each other but they will end up being fast friends.
With yorkies 3 is never a crowd...the more the merrier! I think it helps keep them company especially if they are active and love to play. One of my babies Pochi is a total lap dog and would love to do nothing but sleep in your arms while Choppi the other is very active and runs around and bugs Pochi and Meeju our mini schnauzer. When we got Daisy, she was his match and she's very energetic and active and even tires hims out! Which I think is a relief to the other 2 and even for me.
With 2 or more, I don't feel so bad leaving them home because they will have someone to play with and they won't be lonely. I keep them in the bathroom with food, water, beds and pee pads and they are content.
When we first got Pochi he was our first yorkie and I'd take him everywhere with me but there were times I couldn't and he'd cry and cry and I felt so guilty leaving him by himself but now that they all have each other none of them cry when I leave them at home.
Hope that helps!