they way that's worked in the past (and I see no reason it's changed) is as follows:

patient #1 incurs costs. Insured pays 100% until the $6,000 individual deductible is met.

With a 75/25 coinsurance percentage policy, the insured then pays 25% of costs from $6,000 to $12,000 and it's not until cost go over $12,000 that the policy pays 100%.

** keep in mind that with a family policy, it's entirely possible for you to have to pay 100% of $5,999 for patient #1 and $5,999 for patient #2 in any give year with the insurance company not having to pay out money at all.**