I think it is important to rule out specific conditions such as Ehlers-Danlos syndrome, Loeys-Dietz syndrome, or Marfan syndrome in this context, but there is no reason why generalized advice cannot be beneficial to your health. Just understand that this is poking around in the dark without knowing more about the surrounding context. Hypermobility can be caused by abnormally shaped bone ends, abnormal joint proprioception, or inefficient or defective collagen production. I would focus on making sure collagen production is efficient and normal before testing other possibilities.
Vitamin C is of extreme importance here. Many people have subclinical deficiencies before getting scurvy, but even if you think you get enough, it may be wise to go out of your way to drink more orange juice or supplement regardless. Anything is possible, so you cannot rule out that your metabolism requires more vitamin C than the average person or there is something you are doing that is causing you to waste vitamin C more quickly. Aspirin users need more, for example.
In addition it may be very beneficial to supplement some form of gelatin to obtain the amino acids that collagen and connective tissues are made from through dietary means. I recommend bovine collagen hydrosylate as it does not require cooking like regular gelatin, mixes well in drinks, and will supply the very important amino acid glycine.
Dysfunctions of the thyroid axis are widespread and common and are implicated in basically every kind of disease and ailment that is common in the general population. T3 itself affects virtually every tissue, but thyroid hormones are responsible for creating a cascade of downstream hormones that could have any manner of effects on growth and development. It is most likely of particular importance in this case to ensure adequate production of T3 and to avoid excessive catabolism of tissues from the overactivation of glucocorticoid stress responses, so keep your cortisol and adrenaline low and T3 high. This can be done through avoiding prolonged periods of starvation and frequent intake of salt and sugar, primarily from sources such as orange juice and milk and by adding salt to foods until it tastes bad. Polyunsaturated fats will inhibit the thyroid axis through several effects, such as creating a fatty liver, so keep their intake low. Do not expect collagen production to be fast or normal without a steady supply of T3.