I'm trying to find out the name of a movie. I have no idea who plays
in it or when it was made all I know is roughly the ending. A father
is chasing after his ex-wife and her boyfriend to get his 2 sons back.
The boyfriend instructs the ex-wife to reach under the seat of the
jeep. Under the seat is a grenade which she pulls the pin, blowing
her, the boyfriend, and the 2 sons up. Does anyone know the name of
this movie?

I've never seen the movie but I'm pretty sure that I read the book.  I
think you're talking about "Bitter Blood" by Jerry Bledsoe.  Here's a
link to a synopsis of the book.
http://www.epinions.com/book-review-2647-E2F9CC4-39FD79E7-prod2

If this sounds like the right story, there was a TV movie made of it
called "In the Best of Families: Marriage, Pride & Madness"
Here's a link to it on imdb which includes a somewhat poor review...
http://www.imdb.com/title/tt0110124/

If this is the right story, I suggest reading the book.  I've read
tons of nonfiction.  This was one of the best.  Enjoy.