A Texas family of three instantly grew to a family of seven after a mother gave birth to two sets of identical twin boys at a Houston hospital on Valentine’s Day — a one-in-70 million birth, according to medical experts.

Tressa Montalvo, 36, and her 43-year-old husband Manuel Montalvo Jr. were just trying to give their son one little sister, but instead, they gave him not just one or two … but FOUR little brothers.

Though the pregnancy was planned, Tressa and Manuel said that they weren’t using any fertility drugs. “We planned the pregnancy – I guess we just succeeded a little too much!” Tressa said.

Tressa Montalvo (left) / Manuel Montalvo (right)

According to Reuters, when Tressa was 10 weeks pregnant, her physician told her she was having twins. Doctors detected more heartbeats in subsequent visits, and informed the Montalvos that they were having four babies — not quadruplets, but two sets of identical twins.

On February 14, 2013, Tressa Montalvo gave birth to four healthy boys — Ace, Blaine, Cash and Dylan (in that order) — via Caesarean section. Ace and Blaine were the first identical set and shared one placenta; and Cash and Dylan were the second identical set and shared their own placenta.

“We tried to stick to the A-B-C-D theme when naming them,” she said in a statement. “We didn’t expect it, we were trying for just one and we were blessed with four.”

The odds of naturally conceiving two sets of identical twins is reportedly somewhere in the range of 1 in 70 million. But though extremely rare, delivering two sets of identical twins isn’t totally heard of, ABC News notes:

In April, 2011, Miranda and Josh Crawford of Charlotte, N.C. gave birth to identical twin girls and identical twin boys after undergoing in-vitro fertilization. And in 2002, Christina Tetrick of Wichita, Kan. was pregnant with two sets of identical twin boys, just like the Montalvos.

Believe it or not, even with their house now full, the Montalvos aren’t even done having babies yet. “We want a girl,” Manuel Montalvo said.

Good luck with that!