Yes, Sintra is about 18kms north of Cascais.

https://www.google.com/search?q=sintra+cascais+distance&oq=sintra-cascais+dista&gs_lcrp=EgZjaHJvbWUqCAgBEAAYFhgeMgYIABBFGDkyCAgBEAAYFhgeMggIAhAAGBYYHjIKCAMQABgKGBYYHjIKCAQQABiABBiiBDIKCAUQABiABBiiBNIBCjEyMTA1ajBqMTWoAgiwAgHxBVUCJj41NTj6&sourceid=chrome&ie=UTF-8

Few exiled royals lived in Sintra.
The Counts of Paris had a manor house in the outskirts of Sintra, in Ranholas.

Most exiled royals choosed to live in Cascais and Estoril:
King Umberto II of Italy (Cascais) and his sister Queen Giovanna of Bulgaria (Estoril).
King Carol II of Roumania also lived in Estoril with his second wife Magda Lupescu.
In the 70s, the Counts of Barcelona had a villa in Estoril.
The Hungarian branch of the Habsburgs lived in Carcavelos, near Oeiras, half-distance Lisbon-Cascais.

Cascais was once a small fishermen's village that became fashionnable when King D.Luis I and his son King D.Carlos choosed it for their summer residence in the late 19th century.
The Portuguese aristocracy and haute bourgeoisie followed the RF and built their summer residences along the coast.
Many still exist and remain in the families, f.i. the Duchess of Cadaval's house in Estoril.