I have had custody his entire life. We have a case established with the office of the Friend of the Court in Michigan where I am listed as the custodial parent. The guardianship papers are needed for a benefit that my child was given and will receive regularly as a minor child.
Depending on what you previously secured in Michigan and the type of benefit that your child was awarded, you may be able to transfer your guardianship status to Texas through the same courts that initiate guardianships originally. Or, you may be looking at starting from scratch in Texas. Parents in Texas are considered the natural guardians of the "person" of their children, but are not naturally deemed the guardians of the child's "estate." In Texas, there are dozens of alternatives to formal guardianships, and the benefit that your child receives may very well fit within one of those alternatives.
Sadly, this is unlikely going to be an issue that you can adequately address on your own. At a minimum, I would encourage you to visit with a guardianship attorney near you to discuss all of the facts. I see that you're posting from the Fort Worth area, which I routinely practice in. I offer consultations on matters such as yours at no fee and would be happy to visit with you to elaborate on my answer if you'd like. Feel free to contact me through the link below or through my profile on this site.
This answer does not constitute legal advice. I am admitted to practice law in the State of Texas only, and make no attempt to opine on matters of law that are not relevant to Texas. This answer is based on general principles of law that may or may not relate to your specific situation, and is for promotional purposes only. You should never rely on this answer alone and nothing in these communications creates an attorney-client relationship.
Estate Planning Attorney
James Thomas gave a good answer. Start with determining whether you have a guardianship in MI that will transfer or whether you need to initiate an action in Texas. Also determine whether there are alternatives to establishing a guardianship of the estate. GEs tiend to be time-consuming, tedious and expensive. Depending on the amount of funds involved, using the court registry may be an alternative. Using an 867 trust may also be an alternative, if the amount is large enough to justify. One other option is to be creative. If the funds will not be currently needed, perhaps they can be direceted into a 529 account with a standstill agreement that the funds will not be withdrawn without the permission of the court, and the account will become the child's when he turns 18. That could reduce the bonding requirement.