That sucker branch is from the rootstock, which is some variant of a trifolate. Yes, definitely cut back any rootstock branches, which will aggressively outgrow your satsuma graft, and in doing so, take nutrients and probably kill the scion (by eventual overgrowth and shade). FYI - there is a dedicated citrus forum which is probably the better for future citrus specific questions.

Thank you for the info. Can you give me the name of the dedicated Citrus forum?

The Citrus forum is another Gardenweb forum. https://www.houzz.com/discussions/citrus

I answered this in Citrus forum.