Oh yeah, only the earth's 23.5 degree tilt decides which seasons are taking place in both north and south hemispheres.
However both hemispheres will always remain in opposing seasons in a single continuous pattern dependent on where Earth is in its orbit (N/S):
Vernal Equinox / Autumnal Equinox
Summer Solstice / Winter Solstice
Autumnal Equinox / Vernal Equinox
Winter Solstice / Summer Solstice