"He's a conceptual artist and I'm a collector. So I started looking for art and I saw his art and I went crazy because I really love what he does. Really original," Martin shared. "And then I contacted him."
"And then you collected him," Ellen DeGeneres joked.
"We just got engaged," Martin announced, showing off the ring. "I'm sweating!"
Martin admitted that he was "really nervous" during the proposal.
"I got on my knees," he said.
He then took out a ring in a little velvet pouch in his pocket, he recalled.
"Instead of saying, 'Will you marry me?' I said, 'I got you something!' Bad," the singer said. "Then he was like, 'Yes.' I said, 'I want to spend my life with you,' and he was like, 'What is the question?' 'Would you marry me?' That's it."
Martin said he was so swept up in the moment that it took him 30 minutes before he realized that Yosef had said "yes."
"I'm so happy for you. You deserve that," DeGeneres told Martin.
The singer has been raising twin 8-year-old boys on his own. Yosef, who is Syrian-born and grew up in Sweden, lives with them.
"They love each other. It's perfect, Ellen," the singer said. "It's been really special."
Besides his big engagement news, the former Menudo singer, who is currently on tour, also announced that he will begin a new Las Vegas residency starting next year at the Park Theater at Monte Carlo.