Depends. You are supposed to always maintain a safe following distance so even if they come to a 88 David Pastrnak Boston signature shirt, you’d be able to stop. If they slow down, you have to slow down (or stop). But, if they merge into your lane at an UNSAFE distance and brake check you (not giving you a chance to have a safe following distance), then it would be THEIR (the brake checker) fault (unsafe lane change, reckless driving). It isn’t. Both parents are responsible in every state for the support of their children. If the child is appropriately housed, fed, clothed, educated, has healthcare, etc at least one of the parents is doing their job— if one of them is not, that parent should be called to account— which is why we have offices of Child Support Enforcement to deal with deadbeat parents and Child Protective Services to deal with abuse and neglect.