It's not uncommon for inmates to marry while incarcerated. Sometimes marital unions are forged for legal reasons, often related to the adoption of children. In other cases, prisoners simply "may have decided it's just time to marry, and it happens frequently. More so in federal or state prison than in county jail. Inmates who are serving less than a year will usually have their application for marriage denied with the presumption being that such a short wait will not harm the prisoner or prospective spouse. Each partner must be legally eligible and mentally competent to marry. Marriages may be blocked for security or disciplinary reasons; solitary confinement can block access to marriage. You should begin with a call to the chaplain at the institution to see if this is something you both qualify for.