What little family I have left - my Sister and her family - are all super Christians too. I love my Sister, but after several attempts by her, over the years, to lure me in, I finally closed that book. I wrote her a couple long letters asking her to cease and desist all hints, cards, books, blessings - all that shit.
Writing helps me remember all the points I might forget on the phone, and gave my Sister time to digest the information.

I think she finally got the message this time. We get on fine otherwise - but this stuff was really getting old !

You're going to burn in Hell. Forever. And ever. And ever. At least that's what they believe. I know it's so annoying, so illogical. I'd try asking them how long forever is and challenging that belief. Or you can just draw a line with them.

i Love you very much and I have never attempted to convert you to my believes so when we meet let's just have fun and not discuss religion again. This worked for me ,hope it does for you.