Verbiage alert! Your constructions are too complicated.
Yesterday, I saw the girl I love holding a boy's hand.
Yesterday, I saw the girl I love holding hands with another boy.
I heard that Hector was killed by a gangster.
"I heard that the guy named Hector was killed by a gangster" is correct, but awkward.
There is no need to add relative clauses or participles.
Student or Learner