The Union of two compact sets in ${\mathbb{R}}^2$ with connected complement has a connected complement

In the papers from Chui and Parnes (1971) and Luh (1972), as well on the paper from V.Nestoridis (1996) on the Universal Taylor series, it is used, without proof, that the union of two compact sets in ${\mathbb{R}}^2$ with connected complement has a connected complement. In this work we present a rigorous proof of this fact, by studying some important topological properties of the plane.