Jyeshttah means the Eldest of all. It also means the Oldest of the Oldest.
We know that Brahma is the first created being and he is seen in all the pictures as a older person with white hair. But, Brahma is not THE oldest person. Brahma appears from the Lord’s navel in a lotus flower. So, the creator of Brahma has to be older than him. The Lord is the oldest of the oldest. He created not only the entire cosmos, but even Brahma from whom all the living entities were created.
The Supreme Lord is unborn and ever present. He is always youthful. The Lord completed His appearance on the earth at 125 years as per the material world. He was by then a grandfather, yet He remained ever youthful. We do not see any pictures of the Lord being aged.
Lord Krishna is the master of all living beings and this is described in the Sruti,
Tad aksare parama prajah
The imperishable Personality of Godhead is the Supreme master and father of all living entities.
sarva-yoniṣu kaunteya mūrtayaḥ sambhavanti yāḥ
tāsāṁ brahma mahad yonir ahaṁ bīja-pradaḥ pitā (BG 14.4)
It should be understood that all species of life, O son of Kuntī, are made possible by birth in this material nature, and that I am the seed-giving father.
Krishna clearly explains in this verse that He is the original father of all living beings. The living beigs are a combination of the material and spiritual nature. Living beings are seen in all the planets of this planetary system including the highest planet Brahmaloka where Brahma resides. All the living beings are created from the mother material nature and Krishna’s seed giving process. All living beings get created in various forms and times as per their past deeds or Karma.
advaitam acyutam anādim ananta-rūpam ādyaṁ purāṇa-puruṣaṁ nava-yauvanaṁ ca
vedeṣu durlabham adurlabham ātma-bhaktau govindam ādi-puruṣaṁ tam ahaṁ bhajāmi (Bs. 5.33)
I worship Govinda, the primeval Lord, who is inaccessible to the Vedas, but obtainable by pure unalloyed devotion of the soul, who is without a second, who is not subject to decay, is without a beginning, whose form is endless, who is the beginning, and the eternal puruṣa; yet He is a person possessing the beauty of blooming youth.
Lets chant the Holy Name of the father of all living beings and seek His mercy to remain in His devotional service with true Bhakti always.
Nama 68 – VishnuSahasranama