Three-year-old Joseph McStay Junior and his 4-year-old brother Gianni have been missing for more than three weeks, along with their parents, 40-year-old Joseph and 43-year-old Summer.
"As time goes by it's more and more overwhelming," said Joseph McStay's brother Michael.
Flyers are posted. Family members have searched near the San Ysidro-Tijuana border where the McStays' vehicle was found abandoned four days after they were last seen at their home in Fallbrook.
Now family members are about to get some extra help from Texas Equusearch. The non-profit agency used sonar to look for Natalee Holloway after she disappeared in Aruba.
"This is one of our fully autonomous aircraft," said Mike Hennig, San Diego State University researcher.
Hennig will help fly the remote-control aircraft, equipped with cameras and GPS, to search the area from the Mcstays' home to the Mexico border, looking for the smallest detail.
"Anything that's out of place, a trail or clothing or personal effects," said Hennig.
Originally from Orange County, the McStays moved to San Diego County three months ago.
Family members say there were happy, financially stable and were in the middle of renovating their new home.
What happened is a mystery. The family's two dogs were found wandering in the back yard.
Authorities searched the house last week and gathered possible evidence, but there are no new leads.
"Nothing to suggest foul play or violence and to leave eggs on the counter -- they left the house in haste," said Michael McStay.
Friends and family hold vigils, pray for answers and hope for their safe return.
"I'm grateful for the support," said Michael.