Dude, control your harem, or put an end to it by setting boundaries or straight up choosing only one girl. The other girl is new to the team and they are already having these kinds of arguments in the middle of no man's land, if the relationships get more serious, the arguments will only escalate, and from what they've shown, the little step-sister is even more possessive, so things will only get more complicated once she reaches the right age to join the team. Either put an end to it, set boundaries, keep things professional, or get new team mates. I know it's fiction and the writer will give everyone ridiculous amounts of plot armor to survive any tough encounters, but it's still stupid for them to act this way right after having a near death experience.