BFFs Sofia Richie and Nicola Peltz, along with Nicola's brother Will, returned to Los Angeles from an extended tropical vacay, pets in tow. The trio appeared to be in the Caribbean -- some unknown beachside locale -- with plenty of sexy bikinis in their suitcases for more than enough Instagrams to satisfy their fans.

But what we can't help thinking when we see these two lovely girls together, that they BOTH hooked up with Justin Bieber in the not too distant past. I mean ... they're not the first besties to hook up with the sam guy and they won't be the last. And frankly, if you and your best friend had the opportunity, would either of you turn down the Biebs? Of course not -- so you can't blame the girls -- they were presented with a nice opportunity and they both took it :)

Come to think of it -- as we're looking at our photos, we're now wondering if Ms. Richie didn't jump at the opportunity to hook up with Nicola's brother Will. I mean, they both love dogs, he's cute, she's a girl, he's a guy -- you think maybe those two did the dirty during this trip???