This is a cartoon, so I don't know how many of you have seen it. Anyway, here are my guesses:
Ben Tennyson: ESTP (active, lively, tends to be oblivious to how others feel.)
Gwen Tennyson: INFJ (intelligent, loyal)
Kevin Levin: ISTP (risk-taker, mechanic)
Julie Yamamoto: too minor of a charactor for me to determine accurately, maybe ENFP or ESFP?
Max Tennyson: ISTJ (intergalactic police officer, wasn't a risk taker as a youth, bit of a worrywort, established to be leader of the Plumbers in the latest live-action movie and also the Magister for Earth in the series.)