Kylie Jenner's Stepping Up as Stepmom

Kylie Jenner is arguably stepping up as Tyga's now longtime GF and helping him raise his child ... the other scenario -- she's pissing off baby mama Blac Chyna something fierce.

Kylie took 3-year-old King Tuesday to play a round of miniature golf in Sherman Oaks. Tyga also tried his hand on the putting green.

It's unclear how Chyna feels about her one-time mortal enemy, who she hedged last week during a Facebook Live session.

We're on the lookout for her reaction.