Young Clan Grows Two by Two : Granada Hills: Against all odds, a couple have fraternal twins just 15 months after twin boys. The family now has five children under age 3.

Mark and Thea Anderson feel they’ve been twice blessed--twice. But their responsibilities also are growing at double the usual rate.

After giving birth to her second set of twins in 15 months--the odds of which are about one in 40,000--Thea Anderson left Valley Presbyterian Hospital in Van Nuys on Sunday with the latest additions to the Anderson brood.

The couple now have five children--four boys and one girl.

Their oldest, Devon, is 3.

“We planned on having two kids,” Mark Anderson, 28, said, standing on the toy-littered lawn of his Granada Hills home. “You see how that went. It’s too bad I don’t play baseball. I’d have one hell of an average.”

Twins Adrian and Janae were born Tuesday and weighed in at about 4 1/2 pounds each. Both were healthy. They join Blair and Marric, both boys, who were born in June, 1990.

“People ask me all the time, ‘How did you do it?’ ” Thea Anderson said, looking tired. “I guess we’re just lucky.”

Actually, twins run on both sides of the family. Thea Anderson’s uncles are twins and her husband’s great-great grandmother once shared the world record for being one of the oldest twins alive.

“I think it’s great,” Mark Anderson said of his growing family. “But I may change my mind when they turn 16: ‘I want a car, I want a car, I want a car.’ I haven’t even thought of college. That will kill me.”

Anderson works at his father’s auto body shop. His wife stays home.

Until the latest set of twins was born, the Andersons were unsure whether they would have two boys or a boy and a girl. “I had visions of my own basketball team or my own infield,” the father said. “But my wife is thrilled to have a little girl.”

To make room for the new babies, extra seat belts were installed in the family’s car to secure additional baby seats.

“I still have space for one more,” Mark Anderson said, pointing to an unused seat belt in the middle of the front seat.

Meaning?

He shrugged and grinned.