your pup will be what ever size he will be. 5-10-15 lbs all will be perfect. i have a 15 lb yorkie mix & a 6 lb yorkie. they play together very well, i think mallory the bigger pup knows oliver is smaller & plays accordingly & it's good for oliver the smaller guy to be a little tougher. i was nervous when they were younger & watched them closely & am always aware of their size difference but know now they love each other & never worry about either of them. your pups will be best of friends & i think a 10 lb yorkie is just perfect. dont worry, be happy, ha ha. enjoy your babies great they have eachother!