It's a bit hypocritical of me to say, but I like to see romance as a world building tool, not a plot device. It's something that's meant to add realism to the story, not to make your characters jump through hoops. In real life, a lot of people like to look for and be in relationships, so characters that pursue romance are more relatable. Sometimes, people just like hanging out together, regardless of any external reason or their own motivations and desires.
The key in my mind is to make them comfortable around each other. Maybe they can have moments of tension, or drama, or whatever, but in general, their presence should give them a chance to relax.
Outside of that, yes, communication is important. They should try to make their thoughts and opinions on what's going on clear to one another-
Which is where we get to the 'meat' of the deal. Try to create a web for each character that explains what those thoughts and opinions actually are.
Your MC is the center of a vast web which connects them to partners, potential love interests, friends, family, and others. Each thread of that web represents a relationship, and every relationship is basically a character of its own; one that only exists when two other characters interact.
Now, recognize that every other character has their own web, with completely different thoughts about the same people, and different relationships with them.
Once you have those webs clearly defined, you can start to see how they might interact. Each character will have varying levels of affection for the others. Some of them may end up just being friends, some might be intensely devoted to one or two particular members of the group. That affection may then change their opinions on seemingly unrelated relationships... As if the metaphorical characters that are 'relationships', are also interacting with each other.
It's kinda a big deal. Even just a group of three is three times as much work as a couple. Having four, five, seven people? A lot of work.