They fuck.

"I...I can't," Starfire says.
"Why? You're not allergic to water."
"You're...well, doing the mating dance with my Sister."
"We have no intention of mating, if that's your concern," Lancer replies, "We're just having fun."
"I don't..."
"Let me ask you this- how many times has Blackfire taken or tried to take one of your lovers?"

Starfire blushes and lowers her head.

"Too many to count."
"Well, there's an Earth expression about 'doing unto others what they do unto you.' She's already done that."
Starfire is confused for a moment and then gets it.

She smiles and starts to strip.

https://us.rule34.xxx//images/444/7ff7f859c82ec51ed15f5e7a0066aa4291c4ea52.jpg?443894

She's soon naked- as she only wears underwear when out in battle- and clears the distance between herself and her teammate.

He pulls her in for a hard kiss and she answers it back.
She grabs his ass tightly.
He does the same.

They break the kiss and she goes down to her knees.

"I got a glimpse of your panfarx earlier. This is much better."

She grabs his hard cock and strokes it, before going in to suck it.
'She's good,' Lancer thinks, rubbing her head softly.

After a moment, she stops to ask a question.

"When were you last the with her?"
"Last night. Why?"
"I can tell."

She goes back to sucking.

In the other room, Argent is going down on Blackfire.
She moans happily.

"If they don't fuck, I hope he walks in to see us like this," Blackfire says.

Argent smiles.

"I know they are going to fuck. Maybe he can bring her in to join us," Argent replies.