I don't practice in either Florida or Illinois so this answer is based on general principles rather than specific state rules.
Generally the first question in a guardianship case is why one is needed -- that is why are the parents not able to provide adequate care for the minor. Another way of stating that question is asking whether the minor needs a guardian. If his parents are capable of caring for him and want to do so there shouldn't be any things to look at to permit the mother of his girlfriend in another state to get guardianship of him.
If your boyfriend is in need of alternative care (meaning care outside of his family), your mother would have to file a registration of interest in Florida and ask them to ask for your mother to be homestudied in Illiniois.
In Florida, competent adult residents are eligible to become guardians of a Florida resident ward. A nonresident can become a guardian of a Florida resident only if he/she is related by lineal consanguinity to the ward; is a legally adopted child or parent of the ward;is a spouse of the ward; or is the spouse of a person meeting one of these qualifications. Additionally, Florida does not permit persons convicted of felonies or who have been judicially determined to have committed abuse, abandonment, or neglect of a child to be guardians. These are some of the most important factors the Florida courts take into account.
A person is qualified under Florida Law to serve as a guardian if he or she:
1. Is over the age of 18 years of age;
2. Is a Florida resident; or a non resident who is:
1. Related by lineal consanguinity to the ward;
2. A legally adopted child or adoptive parent of the ward;
3. A spouse, brother, sister, uncle, aunt, niece, or nephew of the ward, or someone elated by lineal consanguinity to any such person; or
4. The spouse of a person otherwise qualified above; and
3. Has never been convicted of a felony.
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