If i paid for adult sons Medical insurance and legal fees but he was living with his grandparents the entir year who can claim him.

[Nonmes]

Also can i keep him on my insurance if his grandparents claim him on their taxes?

[Bsch4477]

You can continue to insure him until age 26. Since he lives with grandparents they get to claim him if otherwise qualified. 

[Nonmes]

According to ACA though it says the individual who claims the dependent  for federal income tax is responsible for insurance. 

I also see it says that for insurance the individual can’t  be the tax dependent of any other tax payer.

[Bsch4477]

That complicates things. Read this discussion. That answer is not clear cut and you might have to discuss with the Marketplace. 

https://www.healthinsurance.org/faqs/we-claim-our-son-but-not-our-daughter-on-our-taxes-how-are-prem...

[Nonmes]

I dont have insurance through the marketplace. It is through my employer and I am having a hard time trying to figure out how that changes things as well.

[Bsch4477]

That makes it simpler. 

Generally, you can join a parent’s plan and stay on until you turn 26 even if you:

• Get married
• Have or adopt a child
• Start or leave school
• Live in or out of your parent’s home
• Aren’t claimed as a tax dependent
• Turn down an offer of job-based coverage