Good same couple slow burn series with cliffhangers

Looking for a good duet series that will follow the same couple and has cliffhangers. I love cliffies! Also, slowburn is heavily appreciated (and preferred). No erotica please! Open door sex is fine and appreciated but just not that too much that it becomes the plot.

Ideally a billionaire romance, like the following:

• {Release Me by J. Kenner}

• {Fixed on You by Laurelin Paige}

• {Bared To You by Sylvia Day}

• {First Touch by Laurelin Paige}

• {Falling In by Lydia Michaels}

It doesn’t have to be billionaire, and can be mafia or just a super protective kinda alpha villain man. No dubcon please

ETA: Angst is very appreciated