What that shows is that the Border Patrol prioritized letting the parent with (apparent) custody keep the child. The child was not deported; rather, the deported father was permitted to take the child with him. The baby, presumably, did not express an opinion.
This would not happen if both parents were US citizens.
That's because neither parent would be subject to deportation if they were both US citizens. Duh.
This means if baby Obama was living with senior he would be sent to Kenya with his alien father when his visa extension was denied.