Child seat frame and compact collapsible stroller

A child seat frame, comprising:

• a seat mount configured to fix to a main stroller frame and having a first latch portion;
• a lower frame having a lower seat frame hub and pivotally coupled to the seat mount, wherein the lower frame has a second latch portion and a lower frame locker, the lower frame locker actuated to engage with or disengage from the first latch portion, and when the lower frame locker disengages from the first latch portion, the lower frame pivots relative to the seat mount;
• and
• an upper frame pivotally coupled to the seat mount and the lower frame, wherein the upper frame has an upper frame locker, the upper frame locker actuated to engage with and disengages from the second latch portion, and when the upper frame locker disengages from the lower seat frame hub, the upper frame pivots relative to the lower seat frame hub;
• wherein the upper frame locker engages with the second latch portion when the lower frame pivots relative to the seat mount.