[Freesurfer] repeated measures ANOVA using the FSGD file

Dear FS expertsTrying to set up a Linear Mixed Effects, which I understand would basically be a repeated measures design. My design has 3 groups (HC, PT relatives and PT).Instead of time points of the same subject my design matrix uses each family member within a family. So I will have many subjects within family_1, same for family_2 and so on... I also want to include gender as a covariate. In short my question is:For my design in repeated measures do I need to define all my groups for each discrete variable as how we do it for glm?For example if I want to have variables GROUP + GENDER + FAMILY.Should i do it as follows?class HC_Female_Family1class PT_Female_Family1class HC_Male_Family2class HC_Female_Family2...... Many thanks,Pablo