When one person's Sun is aligned with the other's Saturn, there's often a sense of weight to the relationship. It feels fated or 'karmic,' with the underlying mood that there's work to do together. This synastry shows up in many longterm relationships. There are built-in feelings of duty and responsibility to the union, and it's a sober one for the hard daily slog of raising kids. It provides a sense of structure for real life, but can be fraught with feelings of obligation and seriousness, too.
The Sun-Saturn relationship is like a crucible with the potential for intense growth. It also has a binding effect that lends itself to commitment. But there are pitfalls to this pairing that trip a lot of couples up. Saturn's limiting, restricting nature puts relentless pressure on the Sun to control what comes naturally. That doesn't sound like fun, but when done in small doses, helps the Sun refine its manner of expression. The Sun finds Saturn disapproving, and may start to feel inhibited under the teacher's judging eye. Saturn as father can be authoritative, and this puts a damper on the Sun's enthusiasm.
Saturn qualities are mature and carefully controlled and directed. Sometimes Saturn grows to resent the Sun, as the lit up embodiment of the energies they keep in check. If Saturn doesn't have a clue about what it's holding back, it can become a control freak over the Sun. The Sun, of course, resents being reigned in, and finds this stifling in relationships.
The Sun-Saturn relationship becomes compulsive when neither realizes what's behind all this posturing. Saturn is made totally insecure by the Sun's ease of expression. A little reassurance from the Sun goes a long way. It also doesn't hurt if the Sun shows respect and appreciation for Saturn's guidance. When Saturn grows self-aware, and learns to admire the Sun for its radiance, both get to bask in the glow.
This is synastry that binds two together, so they'll stick through the hard times. It's a meeting that causes a pair to settle down into the business of living day to day. The Sun warms Saturn, and when it's done right, boosts the confidence of the latter. Saturn is the wizened teacher for the Sun, one that has useful lessons to share from the school of hard knocks. Both have vulnerabilities in this meeting, and only an atmosphere of trust will keep the relationship from buckling under the strain. When there's respect for the strengths and compassion for the vulnerabilities, the bonds between them grow even stronger.