Can I stop my ex from introducing our child to a new partner too soon?

Generally, during their own scheduled time with the child, a parent retains a significant degree of day-to-day decision-making authority over how that time is spent, including decisions such as introducing the child to new people in their life, and Maltese family law does not typically give one parent direct legal control over the other parent's personal choices during their own time with the child, unless there is a genuine, demonstrable concern that this is actually harmful to the child's wellbeing, rather than simply a matter of personal preference or timing you disagree with. If you have specific, genuine concerns that go beyond a difference of opinion about timing or approach, for example concerns about the new partner's suitability or conduct around your child that could actually affect the child's welfare, this is something that could potentially be raised with the Civil Court (Family Section) as part of a broader custody or welfare concern, but a court is unlikely to intervene in ordinary personal lifestyle choices absent evidence of genuine risk or harm to the child. Before escalating this into a legal matter, it may be more productive to raise your concerns directly and calmly with your ex first, since courts generally favour parents working out reasonable day-to-day parenting differences between themselves where there is no genuine welfare concern involved.