Don't understand when " separated from my husband for over two years" and having children-- why did you use Married Filing Separate instead of Head of Household -- assuming that while your divorce is not final, you are living by yourself and maintaining a household for minor children .
If you do not file jointly with anyone else, live as a member of household of another ( your boyfriend) for all 12 months of the tax year, he provides equal / more than 1/2 of your support, he can claim all three of you for purposes of dependent exemption ( zero for 2018 through 2025 ). I do not believe this will make any difference to his refund position. Additionally any available refund will first be used to satisfy outstanding ( court ordered? ) debt , the excess being issued as refund to the taxpayer.
Does this answer your query?
