Adam Senn and Lindsay Lohan are heating up for the holidays.

In related news, The City star has felt a burning sensation when he pees these days.

Lindsay's new boy toy accompanied her to Ali Lohan's 16th birthday party this week.

Once there, "he had his arm around her, was kissing her and stuck by her side,” a source said. “She was glowing. She loves the attention she's getting from Adam and looked extremely pleased with herself for landing Adam — she had a giant smile on her face!"

Witnesses also claim that Ali and mother Dina got into a huge, public fight. But that's par for this troubled family's course.

Adam Senn is totally tapping Samantha Ronson's sloppy seconds and Aaron Carter's sloppy 417ths.

As for Lohan and Senn?

"Adam and Lindsay took smoke breaks together away from the family and he was a total gentleman, holding the door open for her and letting her back walk into the restaurant before him,” the source added.

“Eventually everyone left and Adam and Lindsay stayed behind to spend some quiet time together. They were there until well after midnight, just the two of them. They are definitely having a good time together... she's spending a lot more time in New York than she normally does, just so that she can see him."

Hear that Adam? You owe the Big Apple a major apology.