Speculation has surrounded Robin Thicke with many wondering if he and his 21-year-old girlfriend have gotten secretly married.

On Monday, April Love Geary shared a semi-NSFW photo on Instagram of her backside while wearing an itty-bitty black bikini. However, the bikini bottom has the letters ALT etched into it, which would certainly be her initials if she got married and took the singer's surname.

Her caption didn't temper speculation, either. She simply wrote "his."

Neither April nor Robin have commented on the rumors. To be fair, April is wearing a swimsuit made by company Alt + Swim, so this could all be a simple coincidence. However, the company specializes in producing personalized monogram swimsuits, so customers can create a bikini with any initials they'd like.

Things that make you go, hmmm.

A few hours after her bikini image, she shared another one of her kissing her 39-year-old man that only fueled the fire.

Come with me, my loveeee, to the sea, the sea of love 💙

A post shared by April Love Geary (@aprilovee) on

"Come with me, my loveeee, to the sea, the sea of love 💙," she cryptically wrote.

She does not appear to be sporting a ring in any of her Instagram images.

Robin has not shared any images from the couple's idyllic beach vacation, but he has shared plenty of images of April on his personal Instagram feed.

In late July, he posted an image of her kissing him on a boat.

Love is the most righteous thing.

A post shared by Robin Thicke (@robinthicke) on

"Love is the most righteous thing," he said.

A few months prior he shared another of them cuddling up and looking happy.

April Love and some guy she likes

A post shared by Robin Thicke (@robinthicke) on

"April Love and some guy she likes," he said.

Robin and April began dating in early 2015 when she was just 20 years old. In August 2015, they were hit with engagement rumors, all of which turned out to be untrue. At the time, though, he was reportedly "totally obsessed" with April.

Was he "obsessed" enough to, say, put a ring on it?