Answering some "couple questions" for @viennen about Dash and Leo. Tagging @tiredassmage in case you want to add more.
What do they think of each other's family? And how does the family feel?
For Dash, he doesn't much care for Leo's family, especially considering how they treated Leo in the past. It doesn't help that they're Imperial, on the wrong side in the war in his opinion, and he's heard bits and pieces of how Vorza treated his son. If he ever met the man in real life, he'd immediately punch him in the face. The only one that Dash will actually like if they met is Liv. Mostly, because she's always been close with Leo and supportive of him. I assume that the rest of the family past Liv doesn't even know of Dash's existence. It would be dangerous for everyone if they did.
What's different about their backgrounds? Do those differences affect the relationship?
Leo is a born Imperial, defecting after a couple years in the military, choosing a life as a smuggler instead of enlisting with the Republic. (Dash wouldn't let him anyway, not after what he'd been through). I don't think it changes much about how they work together, how their friendship and romance get on, mostly because Dash doesn't let it define what he thinks about Leo. Because Leo is a good man, he can see that, and he's his best friend. Neither of them would've made it off of Begeren without the other and that's enough for him.
What was their first impression of each other?
Dash saw him as just another Imperial, given their circumstances. Dash was a POW, Leo was one of the Imperials giving him medical inspections during their transfer to the prison. What he didn't expect was to find someone who so deeply despised what the Empire was as much as he did.
How did they fall for each other?
How does anyone fall for someone? They became good friends, relied on each other through hardships, bullshit, gangs on Coruscant. Without Dash, I figure Leo probably would've found himself in more trouble than he liked and with no way to get out of it. Dash found someone he could come home to, someone he was excited to see, someone who wouldn't judge him for the bad things and would celebrate the good with him. Before Leo moved in with him, Dash mostly moved about his day without a care, not bothering to worry what happened to him because who would care past his sisters, his cousin? They were all in this war as soldiers or jedi, and one day, they would bite the dust. It was hard for him to form relationships because of that. But with Leo, he had someone to take care of, someone who gave a shit about him, not the soldier, but the person. And it changed something in him. He felt needed and that was all it took for him to slowly start falling for Leo.
Where is their relationship the strongest?
For Dash, it's in the trust. They trust each other without hesitation, knowing the other will have their back. That at the end of the day, he knows that Leo will be there and he appreciates that.