The only way to be absolutely certain that the person(s) you want to be guardian of your minor children is selected in the event that both you and your partner pass is to have a valid will in place.
When I meet with a potential new Estate Planning client, one of the first questions I hear is, "Do I really need a will?" That question is usually followed by comments such as, "I don't have tons of money," or "If I die, my spouse will just get everything," or "If my spouse and I both die, my parents will raise our kids."
Michigan law starts with the premise that both parents have an obligation to support their children financially. Michigan uses the “Income Shares Model,” which requires child support to be paid based on the needs of the children and the financial resources of the parents. From that baseline, the amount of support can be modified based on several factors, including but not limited to the parenting time arrangement (which parent has the most overnights), and the ability of both parents to earn income (as opposed to actual income earned).