There must be many, since he married twice and fathered a total of 13 children by his two wives. However, only 4 were sons, and only two (both born to his first marriage) survived to adulthood. Of the two, only the elder (who would eventually succeed his father on the throne as King Ludwig I) married dynastically and fathered sons. The younger (Prince Karl) married morganatically and fathered only daughters.
So the royal branch of the house of Wittelsbach, of which he (originally only a duke) was the founder, survives exclusively through the son who became his successor. Interestingly enough, King Ludwig I also fathered four sons; but in his case, all survived to adulthood and married dynastically, three alone fathering sons of their own. As it is, the present-day Bavarian royals all descend from him through his two younger sons. But although he is the nearest common ancestor to them all agnatically, all descend cognatically from his third son (Prince Luitpold, who would eventually serve as regent of the kingdom on behalf of his mentally incapacitated nephews).
I've managed to count six intermarriages involving the descendants of King Ludwig I --
1919: Prince Adalbert of Bavaria and Countess Auguste von Seefried (the union was originally morganatic, but recognized as dynastic by Crown Prince Rupprecht in 1949, when he also de-morganatized the marriage of his son Albrecht)
1921: Prince Konrad of Bavaria and Princess Bona Margherita of Savoy-Genoa
1938: Prince Eugenio of Savoy-Genoa (Margherita's brother) and Princess Urraca of Bourbon-Two Sicilies; neither was a member of the house of Wittelsbach
1950: Prince Ludwig and Princess Irmengarde of Bavaria (the two were first cousins, both descending not only from King Ludwig I, or even from Prince Luitpold, but also from King Ludwig III)
1988: Erich, Prince von Waldburg zu Zeil und Trauchburg and Duchess Mathilde of Württemberg
1991: Duke Friedrich of Württemberg and Princess Marie Caroline, Duchess in Bavaria
But what if the list were extended to intermarriages involving the descendants of King Ludwig I's father, meaning King Maximilian I? Off the top of my head, I can name only two further examples --
1854: Emperor Franz Joseph of Austria and Duchess Elisabeth in Bavaria
1926: the future King Leopold III of the Belgians and Princess Astrid of Sweden
Can anybody name additional examples?