Is it considered a conflict of interest if the judge who sentences someone personally knows the victims involved?

A judge has to be impartial and objective. Personally knowing the victim, could seriosly compromise both.

Usually, a judge will recuse himself or disclose this fact at the beginning of the proceedings. Unless both parties stipulate to the judge maining on the case, the judge should recuse himself.

Additionally, there ar rrules of criminal procedure that provide guidance on how to recuse a judge.  Anyway, unless both parties waived the conflict a motion to recuse the judge should be filed.

Hope this helps