Looking for Jensen: N.D., MN, Raymond Jensen 1917-1985

My grandfather was Raymond Irving Jensen 1917 - 1985. I believe he came from Jensens in the N Dakota area? And is connected to Theif River Falls in MN. I think his mother (my Great grandma) remarried to a man named Weflin after my Grandfather was born. She had also lost a daughter in chilhood at 12 yrs old(?) I have heard while growing up that there was a relative Rudolph(?) Jensen and that the family had a livery stable back in 1800s - early 1900s? I also believe we were related to Lawrence Welk through marriage.I'm looking for any information regarding my Grandpa's lineage. Anyone out there? Grandpa Ray married my grandma, Pearl M Cloutier and they had 4 boys: Rick,(my dad, now deceased) Bob, Ed, and the youngest Jerry (is now deceased). I can find my Grandmother's ancestors but not my grandpa's. Any info would be much appreciated!