W.T.
We cosleep and breastfeed. I have a 2 1/2 year old that isn't a great sleeper and wakes frequently. He's now in his own bed since age two. I also have a 9 month old that cosleeps and nurses and sleeps like a champ. My husband is an awesome sleeper and I am not a great sleeper.
I honestly chalk it up to differences in the kiddos. I guess I honestly don't understand it when people expect their kids to sleep through the night when many adults don't. I am old enough to get up and go pee, get a drink of water, or just try and relax til I fall back asleep. My 2 1/2 year old can't be expected to do that especially when he's developing so quickly physically and mentally and the world is just a stimulating place. He still needs my help and will continue to for a few more years I suppose when it comes to sleeping.
I should add that I nightweaned at 18 months which helped a bit.
Good luck....I think it's just par for the course. We transitioned my son to his own bed right around two. He was ready to go then and we still wake up with him more often than not.