I bet you have completely mixed feelings on this one… fantastic that your daughter found someone she likes and that makes her happy, but as the relationship progresses it becomes more of a worry for you as a parent.
I guess the place to start is to establish how much ‘more’ your daughter wants. I did some research on the views and experiences of intimate relationships in people with learning disabilities (https://link.springer.com/article/10.1007/s11195-017-9502-z) and found that though most people wanted intimate relationships, not all wanted to develop fully sexual relationships. So, finding out for sure how far your daughter wishes to go will be important. Most people feel squeamish asking someone about their sexual needs and desires, particularly when it is a family member, and even more so here in Britain! But, it is a totally natural thing to talk about, and in fact a very healthy thing to talk about if you feel it is something that may cause confusion for your daughter in her relationship. It is easy to overlook the fact that in not talking openly about sex we make those who have not yet been supported to understand many of the issues involved (such as consent, pleasure, respect) more vulnerable than they need to be. Then when they have sexual urges and feelings (as most of us do!) it is inevitably a struggle for some to know how to act and what is ok.
The next thing you will be needed to consider is whether your daughter’s partner wants a sexual relationship or not. Issues of capacity would not need considering if he states he does not want one, as this must be respected. Ideally, this would be something your daughter could ask her partner, but again, this would only be relevant if it had been established that she is looking to take the relationship to that next level. It would be interesting to find out whether the day centre has provided any training or courses around sex and relationships for those that attend, particularly as I assume they are accepting of people developing romantic relationships. If they have not done anything along these lines, or it has not been done for a while, it would be perfectly reasonable for you to request that they do. This may be helpful in starting the conversation between your daughter and her partner, and maybe even you and the parents.
If the partner stated that he does want to have sex, then you may need to consider whether he has the capacity to make the decision, particularly if you feel he has more difficulty understanding things than your daughter. Contrary to popular belief, the bar is not set terribly high in terms of the essential information one must understand in order to meet the criteria to have the capacity to consent to sex. You have to know the basic mechanics of the act, that there are health risks such as STDs, that penile-vaginal sexual intercourse can result in pregnancy, and that both parties must consent to the act – each having the right to say no. Furthermore, just because someone does not know this information at one point in time, it does not mean that it cannot be learnt and retained. Therefore, a person can develop the capacity to consent to sex, given appropriate education/discussion/training.
I suppose this all only becomes an issue when the relationship starts moving in that direction, for example, when your daughter and her partner start to request to spend time in privacy alone together, or to sleep over at one another’s house. The only reason this should ever be prevented is if one or both the individuals lack the capacity to consent to sex, and you believe they will have sex in these situations and that there is an identifiable risk in this. But, people must always be presumed to have capacity unless it is established otherwise. Therefore, should things move in that direction and you or the other parents did have concerns about the partner’s understanding, then you would need to seek an assessment of the partners capacity by a professional (such as a nurse, GP, clinical psychologist, psychiatrist).
A final point, that is not necessarily aimed at your situation Emma, but would be a good one to raise for the wider audience, would be that when people want to be intimate or have sexual needs and are restricted from the opportunity of an outlet for these it can force them to seek out opportunities covertly. One of the most common things I come across in my research into the sexual expression of people with learning disabilities is what I call the ‘lack of privacy leads to a need for secrecy’ effect – denied the opportunity to be alone with themselves or another person, people with learning disabilities all too often have to resort to getting physically intimate with others or themselves in a place or time where those that care for them will not know about it (public toilets and parks are common ones!). Paired with insufficient understanding of what they are doing (owing to inadequate sex education) and a reduced appreciation of risk, this can leave people with learning disabilities unnecessarily vulnerable.
Thank you for your question Emma, I feel like it raised a number of important issues, and I wish your daughter and her partner every happiness!