Eglin Air Force Base, Fla. ? Four-year-old Ava abandons her playmates at school, flying into the arms of Air Force Sgt. Stacia Zachary. The mother and daughter head to the playground.

Their afternoon routine will change in August, when Zachary deploys to Afghanistan for six months and her husband, Air Force Sgt. Christopher Zachary, tackles the solo parenting duties for Ava and her 13-year-old stepbrother. Then in December, dad will deploy and the kids will go to Idaho and stay with an aunt until mom returns.

In a January 2010 photo, Air Force Sgt. Stacia Zachary and her daughter, Ava, 4, play at an Eglin Air Force Base park in Panama City Beach, Fla. after school. Ava is among thousands of children with both parents serving in the military.

Growing numbers of American servicemen and women are married to each other — up 35 percent from 2000 to 2007 — and eight years of war that have stretched the military’s resources mean deployments for both spouses can come in rapid-fire succession.

Many of those couples have children, although the Pentagon does not track that number. For the kids, it means rarely having both parents at home simultaneously. When both are gone, or when duties keep the home partner too busy, extended families often come into play. Kids head to grandparents, aunts or other relatives, sometimes across the country.

It’s a unique sacrifice military families make to combine having a normal life with a state of drawn-out war. It has its own stresses and rewards, couples say.

“In a lot of ways, our children serve, too,” says Stacia Zachary, a combat photographer.

For the parents, it can put added strain on marriages as they spend months apart and worry, like the kids, about a loved one on the battlefield.

“We’ve been married seven years, but we figured that we’ve spent only two and half of those together,” says Christopher Zachary, who serves in the Air Force special forces.

But dual military marriages can also foster closer ties with extended family, and help sustain a solid marriage because fellow soldiers, sailors, airmen and Marines better understand the demands and culture of military life than civilian spouses, couples say.

The Zacharys were among 128,347 active duty and reserve members of the military married to other service members in 2007, the latest year for which Department of Defense statistics are available. That was a 35 percent increase since 2000, when there were 95,336 dual military couples. It does not, however, track the number of children dual military couples have.

With no end in sight to the wars, more military couples are deciding not to put off having children, said Ann Huffman, a psychology professor at Northern Arizona University who has studied dual military couples for the Army. The economy has played a role too — the military offers good paying, steady jobs, and couples are reticent to give up one income in this economic downturn, she said.

Dr. Michelle Freedman, chief of Family and Child Service at Madigan Army Medical Center’s Department of Psychology in Tacoma, Wash., says the center recently saw a lot of 4 and 5 year olds with deployed parents getting kicked out of preschools. Freedman said the kids were acting out because they were upset about changes at home. The worst-case scenario for children who have too much upheaval is an inability to form an attachment to any caregiver, she said.

“But as long as a caregiver is sensitive and loving and nurturing, the children will get through the transitions pretty well. Kids are really very adaptable,” she said.