  The intricate interplay between novel lattice geometry and spontaneous
symmetry-breaking states is at the forefront of contemporary research on
quantum materials. Recently, the observation of unconventional charge and
pairing density waves in a kagome metal CsV3Sb5 brings out a new showcase for
intertwined orders. While electronic instabilities in CsV3Sb5 are widely
believed to originate from the V 3d-electrons residing on the 2-dimensional
kagome sublattice, the pivotal role of Sb 5p-electrons for 3-dimensional orders
is yet to be understood. Here, using resonant tender x-ray scattering and
high-pressure X-ray scattering, we report a rare realization of conjoined
charge density waves (CDW) in CsV3Sb5. At ambient pressure, we discover a
resonant enhancement at Sb L1-edge (2s-5p) at the 2$\times$2$\times$2 CDW
wavevectors. The resonance, however, is absent at the 2$\times$2 CDW
wavevectors. Applying hydrostatic pressure, we find the CDW transition
temperatures to separate, where the 2$\times$2$\times$2 CDW emerges 4 K above
the 2$\times$2 CDW at 1GPa. Our results establish the coexistence of the
2$\times$2 CDW and the 5p-electron assisted 2$\times$2$\times$2 CDW in CsV3Sb5.
The evolution of the conjoined CDWs under pressure suggests the joint
importance of electronic and phononic fluctuations for the double dome
superconductivity.
