Complex sentence: He had a close connection with the Infanta Margarita Teresa of Spain, Leopold I's young wife; the Lobkowicz Collections portrait of the Infanta (attributed to Velazquez) was presumably acquired during Leopold's reign.
Split into simpler sentences: He had a close connection with the Infanta Margarita Teresa of Spain, Leopold I's young wife. The Lobkowicz Collections portrait of the Infanta (attributed to Velázquez) was presumably acquired during Leopold's reign.