Yes, it's possible. But you must show that you;
- lived together constantly for one year (in Belgium or elsewhere)
- or that you've known one another for a minimum of two years.
If you don't live together, you must demonstrate that you've kept in regular touch (by phone, letters, or email). You also have to prove that you've met each other at least three times within the past two years, totalling 45 days at least.
If your partner resides outside the Schengen Area, they need to apply for a type C visa. This is a visa that lets you stay in Belgium for 90 days. Within this time, you must give a statement that you are living together legally.
Do you have additional questions or need more help with your case? You can contact Myria, the federal migration centre, for free legal advice.