Brought home too late?

We brought our new Yorkie puppy home at 18.5 weeks old. It was a breeder. His liter was four. There were seven dogs total at this breeders home. Not knowing any better, and now learning that this is why he may be timid and very difficult to warming up to anyone but me. He loves another family member's yorkie that visits 5/7 days each week. Piddle pad trained easy. Good barker and eater and loves me.
It's been 7 months now.....I want him to love and trust all of us, not just me. Any ideas, guidelines would be greatly appreciated.

I don't know what his problem is but I know what his problem isn't 18.5. I suspect it's just his personality. You could have other family members feed him, walk him, and play with him.

Thanks Bill. My question is related to reading about when to bring a new puppy home, the optimum age being 8 weeks old. Now that my puppy learned to learn with his pack at that formative age, is there any way to teach him to learn from humans. How hard/what methods are used for this?

Yes, but it would be no different than any other dog. All dogs have to be taught how to learn from humans. I like clicker training for teaching dogs most anything. Make any training you do fun and exciting for both you and the dog. There is a lot of room for disagreement about the ideal age to remove a puppy from his litter. 8 weeks is a good age but I prefer 12 weeks. One of the best dogs I ever had was a year and a half old when removed from his mother.

Puppies, in my opinion, should stay with their mother and siblings until close to 12 weeks of age so that they can learn proper doggy manners from their mother and siblings. Puppies who are allowed to stay with their mother and siblings until 12 weeks of age will already know certain doggy manners such as when play-biting how hard is too hard to bite and social cues. At 12 weeks of age a puppy should be able to have some control over their bladder and bowels and they are generally house trained easier. To teach your dog to learn from humans requires patience and consistency. If your dog trusts you but is shy around new people try slowly introducing your dog to new people and situations with you there. Don't coddle your dog if he shows nervousness try to encourage him with your voice and his favorite treats and give tons of praise when he starts to show confidence. Only introduce him to new people/situations one at a time and try not to get him overwhelmed. Always end on a good note and be patient!!! Good luck!!!