Yes you can combine them depending on your research question or objective. grounded theory is somehow embedded in systems theory but depending on the tools u will be using in systems theory, you can combine grounded and systems theory

You could, but the challenge you would then face is how do you reconcile the atheoretical perspective that underpins grounded theory, with the rather well-developed theoretical instruments that Complex Systems Theory puts forward.

Grounded theory is useful for building theory. In my opinion, at least within the social sciences, you can thus combine it with other theories. My own dissertation was an ethnography (based on grounded theory principles) on complex infrastructure systems. If you're looking for ways to 'test', 'measure', or 'hypothesize' certain principles then you may want to seek for another approach. If you want to extend the already existing knowledge with theoretical insights which are grounded in your data, then grounded theory would be one of the ways to move forward.

Combine them as your analytical tools (i.e. use both Grounded Theory and Dynamic Complex Systems Theory in your analysis to figure out how agents in the world employ behaviors to negotiate 'social protection' and 'sustainable peace')?

OR

Combine them in your hypothesis (i.e. hypothesize agents in the world employ behaviors explicable by Grounded Theory and Dynamic Complex Systems Theory to negotiate 'social protection' and 'sustainable peace')?

Fine question. Yes, GT meets DS on case study. Both depart from hypothetico-deductive approach: Article Public-Private Partnerships (PPP) on Moulding State Structur...