In order to qualify for child-in-care spousal benefits:
Like regular spousal benefits, the amount of a child-in-care spousal benefit is 50% of your spouse's "primary insurance amount" (PIA) -- that is, 50% of the monthly retirement benefit that they would get if they claimed their retirement benefit exactly at their full retirement age.
Also like regular spousal benefits, your child-in-care spousal benefit will be reduced if you are simultaneously receiving a retirement benefit. (Specifically, it will be reduced by the larger of your own retirement benefit or your primary insurance amount.)
Unlike regular spousal benefits, you do not have to be age 62 in order to receive child-in-care spousal benefits. In fact, there is no minimum age at all.
Also unlike regular spousal benefits, child-in-care spousal benefits are not reduced for early entitlement. (For example, if a person files for child-in-care spousal benefits 3 years prior to their full retirement age, they'd still get the full amount, whereas a person filing for regular spousal benefits 3 years prior to full retirement age would only get 75% of the full amount.)
Also unlike regular spousal benefits, filing for child-in-care spousal benefits cannot cause a "deemed filing" for retirement benefits. This opens up some strategies for receiving spousal benefits while allowing your own retirement benefit to continue growing.
Example: Bob and Jane are both age 62. Their daughter, Ellen, is disabled and lives with them. Bob has a higher earnings history than Jane. A strategy that is available to them is as follows:
When you lose eligibility for child-in-care spousal benefits (i.e., when your youngest child reaches age 16, if you have no disabled children), what happens depends on your age at the time.
If you are younger than full retirement age when your youngest child reaches age 16, your child-in-care spousal benefit will be suspended. If you are at least age 62 (or when you do reach age 62), you have the option to begin regular spousal benefits by filing Form SSA-25. If you do so, your benefit will be reduced for early filing. When you file Form SSA-25, the normal deemed filing rules will kick in. (That is, you will automatically be deemed to have filed for your own retirement benefit as well, if you had not already done so.) If you don't file Form SSA-25, your regular spousal benefit will still begin automatically upon reaching full retirement age, and the normal deemed filing rules will apply at that time.
If you have reached your full retirement age by the time your youngest child reaches age 16, your child-in-care spousal benefit will simply become a regular spousal benefit (i.e., will continue at the same amount). And the normal deemed filing rules will apply at that time.