Not sure why you changed the numbers in the question, I will be using the original numbers since those are more realistic:
X works for company XXX that offers $600 for Employee and $1,200 for Family.
Y works for company YYY that offers $900 for Employee and $1,500
In order to get the family contribution from the employer, you would have to have "employee+spouse" or "employee+kids" coverage through the HDHP (i.e., "family" coverage).
So, to answer your question, yes. Here is how:
X has a HDHP through XXX and includes x so it qualifies as a family plan. X's HSA gets the $1,200 employer contribution.
Y also has a HDHP through YYY and includes y on their plan. This qualifies as a family plan so they get the $1,500 employer contribution.
Easy as that. Both parents have a family HDHP, separate HSAs, and are both getting the employer contribution. In addition to that, any family member's medical expenses can be payed for through either HSA. This is because an HSA can be used to pay for medical expenses for a spouse or eligible dependent, even if they are not covered by the HDHP. However, there are some caveats:
- The annual family HSA contribution is combined for all family members which are eligible to be reimbursed from the HSA, and employer contributions count towards the annual limit. For the above example, both employers contribute a combined $2,700. If the year is 2019, the maximum that the parents can contribute on top of that is a (combined) $7,000 - $2,700 = $4,300.
- If the parents have separate HDHP plans (as in this example), then they must have separate HSAs as well. In other words, you cannot have both employer contributions go to the same HSA.
- Obvious, but necessary to mention, you cannot double-dip distributions from the HSA. If an expense is payed for through X's HSA, then you cannot take a distribution for the same expense from Y's HSA.
- Since you have separate health plans, you will have separate deductibles. Expenses for a family member will only be applied to the plan under which they are covered. Therefore, it will be more difficult to reach your deductible or out-of-pocket max.
Hsastore.com - Can you have more than one HSA?
IRS Courseware - Individuals who qualify for an HSA.
IRS Pub969 (2018) - Tax-favored health plan rules (2019 version has not been released yet)