My current girlfriend of one year.

Long story short, she brought a house with an ex 2 years ago. He is still on the mortgage.

She is wanting to sell the house. However cos he is still sour about the break up and causing stress for my gf.

Her perants and her want to put my name of the mortgage and take the ex off. This is so he has no control over her life.

However this means I am trapped with debt. The house is too expensive, it's a 30 year mortgage.

I think this is just bad idea, and I should not put my name of the mortgage. It's not my problem.

I don't want her to be in debt, and I have been paying her "rent" because I do stay often.

How to i word it to my gf and her perants without sounding selfish?

Edit: thank you for everyone for the replies. I knew deep down I was always going to say jo, but you guy reinforced it.