Migration flows at the U.S.-Mexico border are increasing for the third time in seven years under Republican and Democratic presidents. Unlike the Trump administration, President Joe Biden has chosen not to expel immigrant children who arrive at the southern border without a parent.

Migrants who were caught trying to cross into the U.S. and were deported rest under a ramp that leads to the McAllen-Hidalgo International Bridge on Thursday, March 18, 2021, in Reynosa, Mexico.

And new rules put in place by the Biden administration mean some families with “acute vulnerabilities” are being released to family in the U.S. and allowed to pursue asylum, while others in almost identical circumstances are not.

Genesis Cuellar, 8, a migrant from El Salvador, sits in a waiting area to be processed by Team Brownsville, a humanitarian group, helping migrants released from U.S. Customs and Border Protection custody, March 17, 2021, in Brownsville, Texas. The group will facilitate travel so that Cuellar, who is traveling with her mother, Ana Icela Cuellar, can be reunited with her brother, Andy Nathanael, 4, and their father Marvin Giovani Perez Bonilla, who have been residing in Maryland after being released from custody. The Cuellar family separated in August of 2020, when they tried to cross the U.S.-Mexico border.

A smuggler paddles a small inflatable raft across the Rio Grande River from Mexico into the U.S. carrying migrant families in Roma, Texas, Wednesday, March 24, 2021.

For migrant children and teens journeying from Mexico to the U.S., there is uncertainty, fear, hope and lots of waiting. On a recent day at a plaza near the McAllen-Hidalgo International Bridge point of entry into the U.S., a deported migrant boy launched a paper plane into the air while playing with other migrant children in Reynosa, Mexico.

A U.S. Customs and Border Protection officer talks to migrants after they were detained and taken into custody, Sunday, March 21, 2021, in Abram-Perezville, Texas.

A migrant woman cries as she talks on a cellphone at a park after she and a large group of deportees from the U.S. were pushed by Mexican authorities off an area they had been staying after their expulsion, Saturday, March 20, 2021, in Reynosa, Mexico.

A family from Honduras sits on the ground after they were smuggled on an inflatable raft across the Rio Grande, in Roma, Texas Saturday, March 27, 2021. Roma, a town of 10,000 people with historic buildings and boarded-up storefronts in Texas' Rio Grande Valley, is the latest epicenter of illegal crossings, where growing numbers of families and children are entering the United States to seek asylum.

A migrant boy (C) launches a paper airplane while playing with other migrant children at a plaza near the McAllen-Hidalgo International Bridge point of entry into the U.S., after being caught trying to cross into the U.S. and deported, March 18, 2021, in Reynosa, Mexico.

A young child walks alone through the brush after being smuggled across the Rio Grande river in Roma, Texas, March 24, 2021.

A migrant child holds onto a woman's arm as they wait to be processed by a humanitarian group after being released from U.S. Customs and Border Protection custody at a bus station, Wednesday, March 17, 2021, in Brownsville, Texas. Team Brownsville, a humanitarian group, is helping migrants seeking asylum with clothing and food as well as transportation to the migrant's final destination in the U.S.

Migrants walk on a dirt road after crossing the U.S.-Mexico border, March 23, 2021, in Mission, Texas.

A 4-year-old migrant boy sleeps next to his father at a shelter, March 22, 2021, in Harlingen, Texas. The father and son were taken into the shelter for the night while they wait for their flight the next morning after they were released from U.S. Customs and Border Protection custody.

A father helps her daughter after they were smuggled on an inflatable raft across the Rio Grande, in Roma, Texas, March 27, 2021.

Migrant families, mostly from Central American countries, wade through shallow waters after being delivered by smugglers on small inflatable rafts on U.S. soil in Roma, Texas, March 24, 2021. As soon as the sun sets, at least 100 migrants crossed through the Rio Grande river by smugglers into the United States.

A migrant child looks through the U.S.-Mexico border wall as a group is processed and taken into custody while trying to sneak across the border, March 21, 2021, in Abram-Perezville, Texas.

Migrant families, mostly from Central American countries, wade through shallow waters after being delivered by smugglers on small inflatable rafts on U.S. soil in Roma, Texas, March 24, 2021.

Migrants families, mostly from Central American countries, walk through the brush after being smuggled across the Rio Grande river in Roma, Texas, March 24, 2021.

Migrants families, mostly from Central American countries, walk through the brush after being smuggled across the Rio Grande river in Roma, Texas, March 24, 2021.

A migrant man, center, holds a child as he looks at a U.S. Customs and Border Protection agent at an intake area after crossing the U.S.-Mexico border, March 24, 2021, in Roma, Texas.

A migrant's muddy shoes are seen without laces as he walks off the customs checkpoint in Reynosa, Mexico, after being deported by U.S. Customs and Border Protection agents, March 18, 2021. Migrants are forced to give up their shoelaces as a security measure after being taken into custody.